Method of making slide fastener stringers



Oct- 29 1946. G. suNDaAcK L 2,410,135 y KBTHD OFIAKING SLIDE FASTBNBR STRINGERS Fned Jah. 1. 194s [N1/Hirn@- Patented Get. 29, 1946 UNITED STATE yMETHOD OF MAKING SLIDE FASTENER STRINGERS Gideon Sundback, Meadville, Pa.

aparcado January 1,1943, serial No. 470,984

in Canada October 21, i942 The invention relates toimprovements in methods of making slide fastener stringers, The slide fastener with which the invention is concerned consists of a pair of stringers, each in cluding a exible tape having a plurality of spaced interlocking members secured to one edge thereof, and a slider, by the movement of which along thestringers the interlocking elements are engaged or disengaged.

An object of the invention is to provide a method for producing the interlocking elements of such a fastener by die casting and to devise a novel method of applying such die cast interlocking elements to the fastener tape by deforma;- tion of the elements in such a manner as to over.. come the tendency ofthe brittle die-cast metal to fracture on deformation.

Yet another object is to'take advantage of th known factvthat certain die cast metals exhibit a tensile strength, in the .as-cast condition, which may. be materially increased by reducing the cross-section oi the casting by compression. By providing a novel design for an interlocking element casting and clamping it on the tape in a novel manner which involves compressive rather than tensile deformation of the casting, a fastener Stringer may be fabricated on which the interlocking elements are even more firmly secured than by casting directly thereon, the only 'presently known method of attaching die cast interlocking elements to a tape.

An additional object is to devise a method of fabricating such stringers which permits the application of a protective or decorative finish to the interlocking elements, for example by anodizing or electrolytically oxidizingan aluminum alloy of which the interlocking elements are made, before application of the elements to the fastener tape,

e crains. I (ci. as me) Fig. 3 isa View similar to Fig. 2 showing the interlocking element clamped on the tape;

Fig. 4; is a view, greatly emerged, taken through the tape of a slide fastener and showing an interlocking element in place ready to be clamped on the tape in accordance with one embodiment of my invention;

Fig. 5 is a view corresponding to Fig. a showing the interlocking element clamped on the tape;

Fig. 6 is a view, greatly enlarged, taken through the tape of a slide fastener showing an interlocking element in place ready to be clamped on the' tape according to a second embodiment of my invention;

Fig. 7 is a view corresponding to Fig. 6 showing the interlocking element clamped on the tape;

Fig. 8 is a View, greatly enlarged, taken through the tape of a slide fastener showing an interlocking element in place ready to be clamped on the tape according to a third embodiment of my lnvention; and

Fig. 9 is a view corresponding to Fig. 8 showing the interlocking element clamped on the tape.

. Like characters of reference designate corresponding parts in the diierent figures.

Referring to Fig. lof the drawing, an orthodox slide fastener comprises a'pair of tapes l, l each having an enlarged edge 2 on which is clamped a plurality of interlocking elements 3. A slider 4 serves to engage and disengage the corresponding interlocking elements of the pair-of tapes. Each tape carrying the interlocking members is ordinarily referred to as a Stringer.

According to conventional methods of making slide fasteners of the type illustrated, the interlocking elements 3 are blanked, or otherwise formed, out of strip or wire stock of nickel silver,

' brass, or any other material which has suicient without subsequent material damage to the nlsh. l

during attachment of the elements.

With the above and other objects, which will hereinafter become apparent as the specication proceeds, in view my invention consists of the method, construction and arrangement, al1 as hereinafter more particularly described and illustrated with reference to the accompanying drawing in which:

Fig. 1 is a fragmentary plan View of a slide fastener embodying the invention;

Fig, 2 is a view, greatly enlarged, taken through the tape of a slide fastener and showing a con'- ventional interlocking element in place ready for clamping on the tape, with the interlocking element clamping tools shown schematically;

malleability to permit the interlocking elements to be clamped on the thickened edge 2 of the. tape without materially weakening and, in some cases, with actual improvement of the strength of, the interlocking elements.

When made by this method, the interlocking elements 3, which consist of a head 5 and a pair of legs 6,6, are formed, as illustrated in Fig. 2, with the legs spread apart to permit the insertion of the thickened edge 2 of the tape I and are clamped on the tape by the action of a pair of tools 1, 'I which, on approaching, bend the legs of the interlocking element together, around original shape results in a combination of com- 'pressive stress on the inside of the leg section and 4 tensile stress on the outside of the leg section.

In the interests of economy, however, and for other reasons which will hereinafter become apparent, it is desirable to make the interlocking stand a definite and very small maximum tensile deformation without fracture, or, if no fracture takes place, without serious` diminution of the strength of the material.

According-to the present invention I obviate this difficulty by casting, by conventional methy or, if not to fracture, at least to be severely weak-` ened. I avoid this by providing an abutment 9 against which the head 5 of the interlocking element may seat while the legs 8, 8 are clamped on the tape by the action of a pair of tools I0, I0, which engage both-the outer side surfaces and the outer end surfaces of the legs 8 and are moved by cam means, or other means, not shown, in a direction to simultaneously swing the legs 8 inwardly and to urge the ends of the legstoward the head of the interlocking element, so that the legs are deformed by compressive action only.

As shown` in Figs. 6 and '7, the same result may be achieved by casting an interlocking element of a novel form, .as shown in Fig. 6, in which the outer surfaces of the legs Il, Il are parallel and in which the head I2 is wider` than is desired in the interlocking element after it has been applied to the tape. This interlocking element is clamped on the tape by the action of tools I3, I3 which are moved toward each other while their surfaces remain parallel and which, as shown in Fig. 1, results in compression of the head I2 only of the interlocking element. It will be noted, of course, that with this type of interlocking element, the configuration of the head I2 before the element is attached to the tape must be such that the changes in shape of the head during attachment to the tape will result in a final configuration, as shown in Fig. 7, which is substantially the same as that of the conventional interlocking element head.

An additional modification of the invention, as

'shown in Figs. 8 and 9. consists of providing an 'interlocking element of whichy the legs I4 are originally straight, but divergent, to receive the tape and which are closed onto the tape by the action of tools I5.' I 5. Such tools contact the legs of the interlocking element over 4their full length, and on closing will becomev parallel, as shown in Fig. 9, to secure the interlocking ele' ment on the tape by imparting compressive stress only to the head and a portion of thelegs thereof.

It will be obvious that,'according to these4 methods of deforming interlocking elements during clamping on the tape. substantially all the stresses 4 developed in the interlocking element will be compressive in nature and, in as much as die casting materials in particular, as well as many other materials, are capable of withstanding much greater compressive stresses thanv tensile stresses, interlocking elements cast from such materials maybe readily clamped on a tape without fracture. Furthermore, as has been pointed out, many of the die casting materials are made substantially stronger. by reducing their area by compression, than they are as cast and the interlocking elements applied, as disclosed, will be substantially stronger even than those which have been cast directly onto a tape. It will also be obvious that this method of attaching die cast interlocking elements to the tape avoids any ob jection to prior methods of casting the elements directly on the tape, involving the tendering of the fabric by the high temperature of the molten metal.

It will also be noted that, `according to the invention, surface deformation of the interlocking element will be spread over an area which is relatively much larger than when the interlocking element is attached to the tape, as shown in Figs. 2 and 3, by conventional methods and, further, such area will be normally concealed in the finished fastener or, at least, will be relatively inconspicuous. This enables a relatively inelastic protective or decorative finish to be applied to the interlocking elements in bulk, such as by electroplating, anodizing in the case of aluminum alloys, and even ordinary enamelling, whereafter the so-treated elements may be applied to the tape individually. In the case of moderately elastic finishes, the deformation of the relatively large surface along-the legs or in the vicinity of the crotch of the element will be insufficient to cause rupture of the surface film, or if, as in the case of anodized finishes, rupture does take place, it will be confined to an area on the element which is concealed from view in the finished fastener.

It may be pointed out that the interlocking elements illustrated before attachment to the tape are shown in the accompanying drawing without the casting runners which would ordinarily be present as the elements are ejected from thev casting die, and that, in particular, such elements would probably be cast in groups of relatively large number, interconnected by a casting runner, inwhich form they may be readily racked and immersed in a liquid bath for electrolytic treatment or other treatment.

What I claim as my invention is:

l. 'I'he method of making stringers for slide fasteners which comprises casting interlocking elements from metal of low tensile strength and having a head anda pair of projecting legs forming a groove between the legs, inserting one edge of a tape in the groove and clamping the interlocking elements on the tape by compressing the metal of theelements sufficiently to bring the.

legs in contact with the tape while pressing on the legs to prevent tension stress in the legs incidental to such compression.

2. I'he method of making stringers for slid fasteners which consists in casting interlocking elements from metal of low tensile strength and having a head and a pair of projecting legs, forming a groove between the legs, placing a tape in the groove and compressing the metal of the interlocking elements to clamp the interlocking elements to the tape while confining the legs to prevent tension stress in the legs incidental to such compression.

melones 5 3. A method for producing stringere for slide fasteners comprising casting a metal which has low tensile strength to form an interlocking element head of sufficient size towithstand inclreceive a tape therebetween, inserting a tape be tween said legs, and compressing the metal in the head to clamp the tape between the legs, so that tensile'stresses which lare developed in the ele- 5 ment incidental to st lch compression are coniined tov said head and are within the elastic limit oi the head.

GIDEON SUlmBACK. 

